Various wireless and non-wireless signals are used to communicate with devices or equipment. Signals can include but are not limited to telecommunication signals, positional signals, data communication signals, sensor signals and other types of signals. Various frequency bands are used for telecommunication signals, positional signals, data communication signals, sensor signals and other types of signals. These signals can create interference among each other based on their frequencies and other characteristics. Accordingly, conventional systems often have dedicated signal paths for signals in different frequency bands.
According to one example of signals, positional signals are used in navigation systems including, but not limited to Global Navigation Satellite System (GNSS). Types of GNSSs include the Global Positioning System (GPS), the Global Navigation Satellite System (GLONASS), the BeiDou navigation system, the Galileo position system and other regional navigation systems.
GNSSs generally use certain signal carrier frequencies for positional signals. For example, the GPS currently uses L1 and L2 signals at frequencies in the GHz range. A foreseen extension of the GPS may include an L5 signal at 1176.45 MHz. Some GLONASS signals are also located in the GHz range (e.g., GLONASS L1 (hereinafter R1) and GLONASS L2 (hereinafter R2)). Table 1 below provides parameters for the L1, L2, R1, and R2 signals. The Galileo System foresees the use of signals centered at the following frequencies: 1575.42 MHz (L1), 1589 MHz (E1), 1561 MHz (E2), 1676.45 MHz (E5a), 1207.140 MHz (E5b) and 1278.75 MHz (E6). Each of the frequency bands shown in Table 1 and listed above may require a dedicated RF receiving circuit.
TABLE 1GNSS Center FrequencyBandwidth systemSigna(MHz)(+/−MHz)GPSL11575.421.023L2/1227.61.023L2 CGLONASSR11602+3.656/−4.219R21246+3.656/−4.219
It is desirable to receive GNSS signals in multiple frequency bands to make the GNSS receiver more versatile and more stable in noisy or occluded environments. For example, conventional GPS receivers have included the capability to receive both L1 and L2 signals so that L2 signals can be used when L1 signals are unavailable. Such receivers have used separate analog processing circuits or have used spatial and time multiplexing to receive both the L1 and L2 signals. The use of separate circuits to receive L1 and L2 signals adds to the size, cost and weight of the receiver. The use of separate circuits also requires separate analog signal paths which adds to the pin count for components within the receiver. The use of spatial and time multiplexing can degrade the resolution associated with the reception of the signal.
GNSS receivers have been integrated in various products, such as, mobile phones, smart phones, tablets, netbooks, laptops, automobile, etc. It would be desirable to include multiple types of GNSS receivers in the products to provide navigation operations with greater versatility and stability. For example, one type of GNSS system may not be available in a particular area or a signal for a certain GNSS may be jammed, and it may be desirable to use another type of GNSS or another GNSS signal. However, the integration of more types of GNSS receivers into products adds to the size, cost and weight of the products. For example, having a separate analog signal processor for each type of GNSS adds to the size, cost and weight of the product. Further having separate analog signal paths for each GNSS and each GNSS signal adds to the pin count within the product and adds multiple analog-to-digital converters (ADCs) to the interface product.